1. Field of the Invention
Aspects of the present invention generally relate to a digital broadcasting transmission apparatuses and a robust stream coding method thereof. More particularly, aspects of the present invention relate to a digital broadcasting transmission apparatus and a robust stream coding method thereof that can be used with a receiving apparatus of a simple structure.
2. Description of the Related Art
The Advanced Television Systems Committee (ATSC) vestigial sideband (VSB) scheme, which is a terrestrial digital broadcasting system in U.S.A., is disadvantageous in that its reception performance is not good in a poor channel environment, particularly, in a Doppler fading channel environment. Thus, the ATSC has accepted new suggestions under preconditions that compatibility with existing receivers is provided, that the existing receivers do not suffer performance depreciation, and that the performance is improved in comparison with the existing receivers in order to enhance the VSB reception performance.
Among the suggestions for VSB system improvement, a dual transport stream scheme enables watching of the existing HD video in a good channel environment and allows for video reception even in a poor channel environment. The dual transport stream scheme generates and transmits a dual transport stream with robust data added to normal data of the conventional ATSC VSB so as to successfully operate in a hostile channel environment.
Hereafter, in reference to FIGS. 1 and 2, a conventional dual transport stream transmission and reception system is described that provides good performance by transmitting and receiving a normal stream and a robust stream and exchanging information by the robust stream.
FIG. 1 is a block diagram of a conventional VSB transmission apparatus, and FIG. 2 is a block diagram of a robust processor of FIG. 1.
Referring first to FIG. 1, the conventional VSB transmission apparatus includes a randomizer 10, a first RS (Reed Solomon) encoder 11, a first interleaver 12, a robust processor 13, a deinterleaver 14, a second RS encoder 15, a second interleaver 16, a trellis encoder 17, and a multiplexer (MUX) 18.
Although it is not shown in the drawing, a dual transport stream (TS), which is the combination of the normal stream and the robust stream, is constructed at the front end of the randomizer 10. The dual transport stream passes through the randomizer 10, the first RS encoder 11, the first interleaver 12, the robust processor 13, the deinterleaver 14, the second RS encoder 15, the second interleaver 16, the trellis encoder 17, and the MUX 18, and then is outputted.
Since the robust processor 13, which is responsible for coding the robust stream, follows the first RS encoder 11, the parity added to the dual transport stream at the front end of the randomizer 10 is not correct. Therefore, the deinterleaver 14 is provided after the robust processor 13, and the second RS encoder 15 is provided to modify the incorrect parity. At this time, the first RS encoder 11 only generates a parity space for interleaving without adding the real parity.
Referring now to FIG. 2, the robust processor 13 includes a symbol interleaver 13a, a normal/robust (N/R) demultiplexer (DE-MUX) 13b, a robust encoder 13c, a robust interleaver 13d, an N/R MUX 13e, and a symbol deinterleaver 1.3f. 
The dual transport stream interleaved by the first interleaver 12 is converted by the symbol at the symbol interleaver 13a, and is separated to a normal stream and a robust stream at the N/R DE-MUX 13b. The normal stream is inputted directly to the N/R MUX 13e. The robust stream is processed at the robust encoder 13c and the robust interleaver 13d, and then fed to the N/R MUX 13e. The N/R MUX 13e multiplexes the normal stream and the robust stream, and the multiplexed stream is converted by the bit at the symbol deinterleaver 13f for outputting.
The conventional VSB receiving apparatus includes a demodulator for processing the dual transport stream received from the VSB transmission apparatus of FIG. 1, an equalizer, a viterbi decoder, a robust decoder, a MUX, a first deinterleaver, an RS decoder, a first derandomizer, a second deinterleaver, a parity eraser, a second derandomizer, and a robust packet DE-MUX. The robust decoder includes a TCM MAP decoder (TCM refers to trellis code modulation; MAP refers to maximum a posteriori probability.), a robust deinterleaver, a robust MAP decoder, a robust interleaver, a frame formatter, and a symbol deinterleaver.l Information exchange is conducted through a loop formed between the TCM MAP decoder and the robust MAP decoder until sufficient performance is acquired. Upon the completion of the information exchange, the data output from the TCM MAP decoder is used for receiving the normal stream, and the frame formatter forwards the data output from the robust MAP decoder to a position corresponding to the robust stream of the normal stream and the robust stream. In doing so, the empty position corresponding to the normal stream is outputted via the symbol deinterleaver 3f to be used for the robust stream reception.
As discussed above, when the conventional VSB transmission and reception apparatuses add the robust coding, such as a ¼ rate coding, to the robust stream using the robust encoder 13c, the VSB receiving apparatus should be constructed in accordance with the structure of the VSB transmission apparatus. As shown, the VSB receiving apparatus has a complicated structure.